1. Field of the Invention
The present invention relates to a playback apparatus for playing back information from a recording medium in which, in a data structure including sync signals added in units of data items each having a predetermined size, the information is recorded in runlength limited codes, and the sync signals correspond to a plurality of consecutive sync-signal-unique run lengths, and to a sync signal detecting method therefor.
2. Description of the Related Art
Examples of the related art are disclosed in Japanese Unexamined Patent Application Publication No. 2001-243727, and Japanese Patent Nos. 3697809 and 3377669.
Technologies for recording and playing back digital data include, for example, data recording technologies in which optical discs, such as a CD (compact disc) and a DVD (digital versatile disc), are used as recording media.
Optical discs include playback-only types which are known as a CD, a CD-ROM (CD read-only memory), a DVD-ROM (DVD read-only memory), etc., and in which information is recorded in embossed pits, and user-data-recordable types known as a CD-R (CD recordable), a CD-RW (CD rewritable), a DVD-R (DVD recordable), a DVD-RW (DVD rewritable), a DVD+RW, and a DVD-RAM (DVD random access memory). In the recordable types, data can be recorded by using magneto-optical recording, phase-change recording, pigment-film-change recording. The pigment-film-change recording is also called “write-once recording”. The pigment-film-change recording is suitable for uses such as data storage since data can be recorded only once and may not be rewritten. In addition, the magneto-optical recording and the phase-change recording, data can be rewritten. Accordingly, both are used for various uses such as recording of content data of various types such as music, video, and application programs.
Furthermore, in recent years, a high-density optical disc, called a “Blu-ray Disc™”, has been developed, and has a greatly large storage capacity.
On the above optical discs, information is recorded in forms such as embossed pits, pigment-change marks, and phase-change marks. In the following description, these marks are generically referred to as “marks”, including the embossed pits. In many cases, marks on the discs are formed on the basis of signals obtained by modulating the original data (to be recorded) into runlength limited codes.
Recording formats of the discs employ a data structure in which sync signals are added in units of predetermined data items. Accordingly, by detecting a sync signal, timing for demodulating data and an address can be obtained.